Various header fields are defined as structured fields but with
unstructured portions; those portions may of course contain parentheses
(not necessarily balanced) which should not be interpreted as comments
(or, in fact, at all). That includes RFC 1894 Original-Envelope-ID,
Reporting-MTA, DSN-Gateway, Received-From-MTA, Remote-MTA,
Original-Recipient, Final-Recipient; RFC 2298 Diagnostic-Code,
MDN-Gateway, and probably Reporting-UA (there is an ambiguity in the
Reporting-UA ABNF, but that does not affect this issue).
these are not message header fields; they are part of specific
content-types. surely you don't think that the 822 syntax should
be applied to message bodies also?
Keith